Pakistan's Prime Minister Nawaz Sharif, in a telephone call on June 16, urged Afghan President Hamid Karzai to help stop militants from fleeing as Pakistan continues its military offensive in a border region.

The North Waziristan region has long been a stronghold of Taliban and other militants who use it as a base to launch attacks against NATO troops in Afghanistan.

Afghanistan and Pakistan have accused each other of failing to act against the militants.

Pakistan launched its latest offensive on June 15, a week after militants attacked the Karachi airport, killing dozens.

General Joseph Dunford, the top U.S. military commander in Afghanistan, has told AP that the United States has increased its surveillance over the Afghan-Pakistani border but that so far officials have not seen any militants fleeing the latest offensive.